This invention relates to timing chamber ignition as it is disclosed and claimed in my U.S. Pat. No. 4,977,873 issued Dec. 18, 1990, entitled TIMING CHAMBER IGNITION METHOD AND APPARATUS. And, this invention is to be distinguished from prior art commutated high tension spark ignition systems. A characteristic feature of the Timing Chamber Ignition concept is the employment of a separate timing chamber and igniter means exposed therein, and all of which is in open communication with the combustion chamber of the engine. That is, a passageway enters the engine combustion chamber and openly communicates with a closed timing chamber having a timing zone into which a compressed fuel-air mixture pressure front penetrates during the compression cycle of the engine operation, and having a buffer zone that responds to said pressure front penetration as a gas spring, there being igniter means at a level or pressure front position corresponding to the point at which the ignition is required for optimum engine performance. The buffer function is variable, and the timing chamber displacement is adjusted and/or controlled for a particular engine performance, so that optimum ignition timing is established therefor. A feature is the response of the igniter means in the timing zone of the ignition chamber, to the fuel-air density as a result of throttle conditions. There is a gas shield effect at a stratified pressure front that precludes pre-ignition while inherently timing ignition in response to dynamic pressure conditions within the combustion chamber. Accordingly, this Timing Chamber Igniter Plug automatically adjusts to engine operating conditions. In practice, the igniter means is a heated element positioned where optimum ignition of the pressure front is to occur, the igniter means being electrically energized with a suitable low vehicle voltage. As shown, this Timing Chamber Igniter device has the external configuration of and resembles a conventional prior art spark plug. However, the internal features thereof are distinct from any spark plugs by the absence of any electrodes and by the provision therein of an ignition chamber and an igniter strategically placed therein.
Internal combustion engines employ the Otto spark ignition, carried out in various forms of engines which are recognized conventionally as either two cycle or four cycle, including reciprocating as well as rotary engines. This invention is particularly concerned with engines which employ compression to heat a combustible admixture of gas and air, followed by timed ignition thereof and heretofore produced by a high tension electrical discharge system with commutation to the multiplicity of spark plugs involved, and employing step-up coils, condensers and breaker points, all combined in a complex system using both low and extremely high voltage electricity. Thus, the prior art has resorted to complex and expensive means, all of which is eliminated and replaced by the simple relatively inexpensive Igniter unit herein disclosed. It is a general object of this invention to provide a commercially practical and improved ignition plug of the type under consideration, to replace the conventional spark plug configuration without any change or modification to the engine, except to remove uneeded systems as suggested above.
The ignition system herein disclosed is universally applicable to internal combustion Otto cycle engines of all types. That is, this ignition system is operable in carbureted or atomized fuel injected Otto cycle engines, regardless of the type of fuel employed, providing a stoichiometric ratio of fuel to air exists that will support combustion. Therefore, it is a primary object of this invention to provide an igniter plug with improved and durable igniter means for timed ignition of internal combustion engines, and by providing igniter means maintained within a temperature range that ensures ignition of the fuel-air mixture without misfiring. A feature of the igniter means is that an ignition element in the form of a high temperature heater is suspended in the timing chamber spaced at the juncture between the timing zone and the buffer zone, as will be described. In present practice the heater is maintained within a temperature range of approximately 1000.degree. to 2000.degree. F. for predictably optimum results with presently available fuels. Responsive ignition by the heater normally occurs before top dead center of the engine crank motion, by touching a stratified pressure front from said compression mixture brought into contact with said high temperature heater.
With this invention, there is progressive movement of the pressure front into the closed chamber, preferably an elongated ignition chamber that is penetrated by the pressure front to the position of the igniter means. At this pressure front level and/or position within the closed chamber, ignition occurs and projects a torch into the engine chamber, it being an object of this invention to control pressure front penetration by changing or varying the spring rate of the buffer zone. Volume of the buffer zone is a primary factor that determines pressure front penetration, and the cross sectional area along the buffer zone is a controlling factor. In practice, the buffer zone is a continuation of the timing zone and is basically of a fixed volume. The gas spring formed thereby has the elastic effect of the gas or gasses that are compressed, these gasses responding according to their displacement ahead of the penetrating pressure front. Therefore, the cross sectional area of the timing zone (also of the buffer zone) is varied as by being tapered so as to augment or to diminish the spring rate as may be required. It is also an object of this invention to vary timing chamber volume by valve means, for example by a solenoid operated valve means.
This timing chamber igniter unit as it is disclosed herein is conductive to operation with lean fuel-air mixtures, which heretofore have been regarded as un-workable. That is, the conventional stoichiometric ratio can be reduced from the usual 14 to 1 ratio to a far leaner mixture which otherwise would destroy conventional spark plugs. With the present invention however, the penetrating stratified pressure front of leaner mixture touches the igniter means heater and following which flame torch progression is toward and emanates into the engine combustion chamber. In accordance with this invention, the igniter means heater is fabricated of a noble metal having catalytic properties such as Platinum, Paladium or Rhodium. These catalysts speed up and enhance the chemical oxidation process of burning the fuel-air mixture without consuming themselves, which ensures a long igniter life. However, the use of such noble metal for the heater does not preclude the use of less expensive materials such as nickle chrome wire and the like, when requirements permit.
As thus far described it will be observed that this invention involves a dyamic timing catalytic ignition (DTCI) system, devoid of the conventional spark ignition. Accordingly, it is an object of this invention to provide prechamber catalytic enhancement of the combustible mixture combined with compression timed ignition, inherently devoid of other mechanical or electrical timing means.
It is an object of this invention to intensify instantaneous ignition by means of a compression responsive igniter. To this end a catalytic prechamber is employed in combination with a compression responsive timing chamber. A feature is a timing chamber wherein a catalyst is placed so as to enhance the gas ignition phase and burning of the remaining mixture in the engine combustion chamber. This is accomplished by a powerful flame torch which emanates from the timing prechamber. Heretofore, catalytic prechambers have been unable to time ignition per se, so that Otto cycle engines have relied upon spark ignition, and Diesel cycle engines have relied upon timed fuel injection. However, the catalytic prechamber concept has advantages and is compatible with the timing chamber ignition concept of my aforesaid U.S. Pat. No. 4,977,873. Accordingly, the timing chamber herein disclosed includes prechamber features in the form of a catalytic element of noble metal over or through which the stratified combustible mixture pressure front penetrates on its excursion to the igniter means. Again, the igniter means is a heater preferably of a noble metal as above specified, preferably Platinum.
The catalytic ignition concept is suited to the ignition of conventional and presently available premixed high octane fuels. A high temperature, homogeneous charge environment consisting of gasoline and air is naturally well suited to in-cylinder catalytic treatment and a catalytic prechamber is attractive from the standpoint of controlling all phases of in-cylinder combustion. Such a prechamber influences both chemical and gas dynamic processes; it regulates contact between the fresh charge and the catalytic element; it allows activation to take place in a well defined volume open to the igniter means; it provides means to control catalytic surface temperature; and it intensifies burning of the non-activated portions of the mixture.
To understand the potential of catalytic activation as a means of enhancing gas phase combustion requires understanding the roles of species and thermal activation. This distinction is complicated by the fact that hot products leaving the catalytic surface promote homogeneous production of the same chain-branching species that might be attributed to species activation. The theory of catalytically assisted homogenous combustion framed here is based on thermal activation principles. Catalytic combustion can be modeled as two distinct processes. The first is catalytic surface reaction and the ensuing diffusion of radicals as well as heat into the homogeneous phase. The second is the effect of these reaction by-products on the combustive properties of a gaseous hydrocarbon mixture. In as much as catalytic reaction is mass transfer limited, surface reaction rates can be estimated by well established mass transfer correlations. As to the effect of thermal activation, Heterogeneous catalysis is unique in its ability to selectively oxidize hydrocarbon mixtures to final reaction products and to thermally activate the remaining charge in the surrounding gas phase. Note that in non-catalytic systems it is nearly impossible to bring about controlled prereaction. Empirical observation has shown that thermal activation by catalytic prereaction will provide a twofold increase in flame velocity and a 50% reduction in ignition energy requirements, when observed under reasonably adiabatic conditions. Even with a 50% heat loss, flame velocities are 25% higher than with no catalytic prereaction. Thus, thermal activation by hetrogeneous catalysis bolsters the laminar flame velocity and reduces the required ignition energy and is most useful.
It is an object of this invention to concentrate the effects of catalysis in a relatively small volume timing prechamber responsive to a stratified pressure front of combustible mixture. The timing prechamber serves to activate only a small portion of the total mixture under compression. Ignition and burning of the total mixture is achieved by a powerfull flame torch which emanates at the igniter means heater and from the timing prechamber opening into the combustion chamber. This gas dynamic function brings about complete combustion of the total mixture including the unactivated portion thereof.
Heat dissipation is a factor to be considered in the manufacture of this Igniter unit, much the same as is the heat range control a major consideration in the spark plug art. That is, the deciding factor in the choice of proper spark plugs is the thermal value, which is controlled by the ceramic insulator design and its relation to the metalic body threaded into the combustion chamber of the engine. Although the Igniter unit of the present invention is not subject to critical spark gap problems, ignition temperature is of some concern so that pre-ignition will not occur. To this end the igniter means of the present invention is thermally isolated from the surrounding structure of the timing chamber, and the timing chamber passage is comprised of a structure that is isolated from the body of the unit. In practice, the timing prechamber and passage structure is a heat isolating insulator of ceramic material that also dissipates heat. As a result, passage temperature is held below 600.degree. F. for example, while igniter means temperature ranges from 1000.degree. to 2000.degree. F. Accordingly, it is an object of this invention to control internal heat conditions and to dissipate heat absorbed from the combustion process, so as to preclude pre-ignition and to ensure the timed ignition which is inherent with the use of this timing pre-chamber and igniter means. Another feature of this invention is the heat insulating dielectric rod that carries the igniter means heater, an object being to isolate this heater from the surrounding unit structure.
The foregoing and various other objects and features of this invention will be apparent and fully understood from the following detailed description of the typical preferred forms and applications thereof, throughout which description reference is made to the accompanying drawings.